For the US, 1/2 in. gap would be the max you'd want to space the deck boards - horizontally speaking. See picture below - those planks are spaced at 1/2''. This goes for any type of decking (pressure-treated wood, composite decking, concrete planks, etc.) This page on our site is geared towards ADA compliance with our

Would you call out the spacing between these TREX boards? The underneath the boards are very wet. Would you call the size of these joist hangers on th. decking must be gapped, both end-to-end and width-to-width. Gapping is necessary to facilitate drainage and for the slight thermal expansion